|
Page 2
<br /> December 20,2023
<br /> Brusca File No. 260-004 Groundwater Monitoring Wells Workplan
<br /> SITE DESCRIPTION AND BACKGROUND
<br /> A 1,000-gallon diesel UST was previously located on the westerly portion of an approximate 140-
<br /> acre parcel situated directly southerly of East Comstock Road and about 2,400 feet easterly of Jack
<br /> Tone Road in Linden, San Joaquin County, California. The majority of the parcel supports
<br /> farmland comprised of orchards. The UST was situated within the Anderson Barngrover farm
<br /> facility, directly easterly of an older, sizable walnut huller building and westerly of an office
<br /> building (converted residence) associated with the farm (see Plate 3). It is indicated that the UST
<br /> was an exempt farm tank and neither San Joaquin County permitting nor regulatory oversight was
<br /> required or provided for the UST removal. Following tank removal, the UST pit was backfilled for
<br /> safety reasons with soils obtained onsite.
<br /> Laboratory testing of soil samples collected at the time of UST removal revealed than an
<br /> unauthorized release(s) had occurred from the UST system; it is reported that diesel-range
<br /> petroleum hydrocarbons and related volatile organic compounds (VOCs), including benzene,
<br /> ethylbenzene, xylenes, and naphthalene, were detected in soil samples collected beneath the
<br /> UST. Since that time, our firm has conducted investigations to evaluate the nature and extent of
<br /> subsurface impact conditions attributable to the former diesel UST, including a number for
<br /> exploratory borings for soil and groundwater sampling, soil gas sampling, performance of a water
<br /> well survey, sampling of the onsite water supply wells, and comparison of site information to Low-
<br /> Threat Closure Policy (LTCP) criteria.a 3 4 s 6 The locations of our borings are shown on Plate 3.
<br /> Reference is made to the cited reports for details regarding the past investigations and the
<br /> laboratory data.
<br /> Our most recent referenced report (dated October 31, 2023) suggested that the limits of the
<br /> groundwater plume were reasonably defined and that the site generally meets LTCP criteria for
<br /> UST case closure. CVRWQCB indicated concurrence via email on November 16, 2023.
<br /> However, upon further consideration and per the referenced December 12, 2023 letter, the
<br /> CVRWQCB subsequently determined that additional site assessment is necessary, including
<br /> further evaluation of the extent of the diesel groundwater plume to the west and installation of
<br /> groundwater monitoring wells to evaluate the groundwater flow direction, plume stability, and
<br /> whether non-aqueous phase liquid(NAPL) is present.
<br /> 2 Brusca Associates, Inc.; "Soil Investigation, Area of Removed Underground Fuel Tank, Anderson Barngrover
<br /> Ranch Property, APN 091-030-130m 14290 East Comstock Road, Linden, San Joaquin County, California"; April
<br /> 7,2023.
<br /> 3 Brusca Associates, Inc.; "Additional Site Investigation, Area of Removed Underground Fuel Tank, Anderson
<br /> Barngrover Ranch Property, APN 091-030-130m 14290 East Comstock Road, Linden, San Joaquin County,
<br /> California";June 8,2023.
<br /> 4 Brusca Associates, Inc.; "Additional Plume, Area of Removed Underground Fuel Tank, Anderson Barngrover
<br /> Ranch Property, APN 091-030-130m 14290 East Comstock Road, Linden, San Joaquin County, California";
<br /> September 11,2023.
<br /> s Brusca Associates, Inc.; "Additional Plume, South of Former Underground Fuel Tank, Anderson Barngrover
<br /> Ranch Property, APN 091-030-130m 14290 East Comstock Road, Linden, San Joaquin County, California";
<br /> October 31,2023.
<br /> 6 State Water Resources Control Board; "Low-Threat Underground Storage Tank Case Closure Policy"; effective
<br /> August 17,2012.
<br />
|